Flashcards in Lens and Cataracts Deck (70):
Describe the anatomy of the lens
Cellular laminated avascular capsule
Inner nucleus is dense and water insoluble
Outer cortex is water soluble alpha/beta crystalline fibers
Anterior epithelial layer between cortex/capsule
Lens capsule is the basement membrane by epithelial cells
Describe the composition of the lens
Dehydrated structure 65% water and 35% solid
85% of solids - soluble alpha and beta crystalline fibers from the cortex; 13% are insoluble albuminoids, 2% gamma crystalline fibers in the nucleus
What is the purpose of the lens metabolism?
Clarity of lens
Briefly, talk about the biochemistry of ions and proteins in the lens
High potassium; low sodium
Proteins mostly responsible for whether or not lens remains clear
What is the definition of a cataract?
Any congenital or acquired opacity in the lens capsule or substance irrespective of the effect on vision
Can happen with aging and is common, can manifest as leukocoria
What are some congenital causes of cataracts?
Ocular maldevelopment (Peter's Anomaly)
What are some causes of acquired cataracts?
Trauma (Blunt, radiation)
Genetic late onset
Describe developmental cataracts
Congenital or formed early in life, don't usually interefere with vision (a technically opacity)
Name the many kinds of developmental cataracts
Anterior polayer (pyramidal)
Persistent Hyperplastic Primary Vitreous (PHPV)
Describe a congenital nuclear cataracts
Tiny white dot
Located in the center of the lens
Formed by loose epithelical cells getting caught during lens vessicle formation
Rarely affect vision if eveer
Describe an anterior polar cataract (pyramidal)
Occurs in 4th week as lens vessicle pinches off surface ectoderm
Opacity on the front surface of lens capsule
Cataract has pyramidal shape with apex pointing out into AC
No VA effect
Describe an Umbilical Cataract
If during 4th week of development posterior epithelial cells do not become primary lens fibers then nucleus never forms, a collapse and opaque lens forms
"Umbilicated - like a red blood corpuscle"
Describe an Axial fusion cataract
Lens fibers diying while they mitigate forward
Opacity forms anterior to posterior going through many layers of the lens
Describe Sutural Opacities
Form when the lens fibers do not meet properly and cause an extra space that's filled with an albuminoid substance
Describe a coralliform cataract
Sutural opacities with an irregular coral shape, aggregated sutural opacities that combine
May or may not affect VA
Describe a persistent hyperplastic primary vitreous cataract
Forms in the 7th month of development and avascular
Hyaloid vasculosa (primary vitreous) can persist and pervent lens growth --> small lens that's opaque and still vascularized
Can result in leukocoria
Can see Mittendorf Dots too, reminants of PHPV on the back of the lens
Describe a tunica vasculosa lentis
Form of PHPV; unilateral and noticed in neonatal period
Associated with micropthalmos, lens may be cataractous
IOP may be high
Elongated ciliary processes are visible through dilated pupil
B-scan confirms the diagnosis in presence of a cataract
What is a Lens Coloboma?
Tertiary vitreous fail to form --> lens will be subluxated
May form due to iris coloboma or Marfan's syndrome
Describe a lamellar cataract/zonular cataract
Due to calcium levels droping then restoring causing opacification and clearing
In young children the opacity are large and with age appears smaller as it's pushed towards center of the lens
Can appear as spokes/riders
What is a Galactosemia cataract?
Developmental cataract, rare and bilateral condition
Caused by lack of enzymes to metabolize galactose in GI tract
Cataract is right below lens capsule
Condition may reverse if caught early enough
What are the two kinds of galactosemia cataracts?
Deficiency of Galactokinase - only involves formation of cataracts
Deficiency of Uridil Transferease - More common, mental retardation if milk continues to be ingested "failure to thrive"
What is spherophakia/microspherophakia
Congenital variant and child is born wit ha small highly convex lens that is almost spherical in shape
Results in very high myopia
May cause pupillary block, lens bulging forward and blocking the aqueous
What is lenticonus?
Lens capsule too thin and causing a cone line protrusion of the lens
What are the signs of lenticonus?
High myopia, high irregular astigmatism
May occur anteriorly or posteriorly
What is lentiglobus?
Much larger area affected but otherwise it's lenticonus, entier posterior lens can be bulging for example
What is a Senescent Cataract?
The most common and inevitable cataract due to decrease in lens metabolism, an aggregation of proteins and Na/K atpase slows down.
What are common patient complaints for senescent cataracts?
Smoky hazy vision
Not a sudden loss of vision, no VF loss and no pain
What are the three kinds of senescent cataract?
Describe a Cortical Cataract (Cuneiform)
Varied effect on VA
Glare or monocular diplopia
Slow/rapid progression possible
Vacuoles, water clefts and spoking
What is the clinical presentation to a cortical cataract?
Water vacuoles, clefts (between lens fibers due to hydration of cortex)
Describe the progression of a cortical cataract
Lens metabolism decreaes via age, Na/K ATPase slows, now sodium is low and potassium is high
Cationic shift causes water to enter and lens to swell
Water enters through semi-permeable laminated capsule and comes in contact with water soluble proteins in outer cortex
Describe the pathophysiology of the cortical cataract
A and B crystalline fibers dissolve forming opaque aggregates
Cortex becomes gray and white, beginning to opacify.
# of amino acids is increasing and pH of lens decreases
Cathepsins (proteolytic enzymes) activated and change the pH
Lens starts to shrink
What are the four stages to a cortical cataract?
Inturnescent (Phakomorphic/Phacogenic GLC)
Describe the Incipient stage of a cortical cataract
First stage; see water vacuoles under lens capsule
Describe the intumescent stage of a cortical cataract
Lens takes in more water, mature cataract that is swollen
Opacification of lens fibers
Lens may look fairly clear with VA only slightly affected
Lens is bigger with some spoke formation
Can lead to secondary glaucoma
Describe the mature cortical cataract stage
All fibers are obaque and the lens is starting to shrink, VA starting to decrease
Describe the hypermature cortical cataract stage
Continued development of mature cataract
Caused by degenerated protein leakage of the liquefied cortex out of the lens capsule
Lens is smaller than normal size and shrivelling
May lead to secondary glaucoma
Not an inflammatory condition
What is the name for a hypermature cataract?
Morganian cataract; lens is completely liquefied and nucleus sinks inside the lens capsule
Describe a posterior subcapsular cataract
Under posterior lens capsule and start centrally and move peripherally
Due to the normal aging process or trauma, steroids and diabetes
Can cause a profound VA loss by sitting on the nodal point of the eye, especially in high illumination
What is a posterior subcapsular cataract called in a younger patient?
Describe a cupuliform cataract (PSC in young patient)
Glare or lower VA, miosis, near > distance affected
Secondary to trauma, steroids, inflammation, Diabetes, ionizing radiation
Best seen with retroillumination
Describe the nuclear changes in the lens
New fibers made at outer portion of lens, push inward and compact together into a hardened nucleus
UV radiation causes biochemical changes causing accumulation of phosphorescent chromophors and can cause nuclear sclerosis
Lens hardens, yellows with time and becomes less elastic leading to presbyopia
Describe a nuclear cataract
More predictable age wise, regular progression
Variety of patient complaints and many different refractive indices in the lens now
What are the signs for a nuclear cataract?
Refraction with NO end point, yellow nucleus, myopic shift "second sight", monocular diplopia
What are the colorations of nuclear cataracts
Yellowing - urochrome pigment
Brunescent - opacity is brown and usually at the advanced stage
Cataract Nigra - black colored cataract
What are normal age-related changes in nuclear cataracts?
Some degree of yellowing is normal
Excessive is a nuclear cataract
Progress is slow and usually distance affected more than near
Poor hue discrimination, especially with blue
Lenticular myopia, the increase in lens refractive index, IE second sight
Give the AOA classification of a Nuclear Cataract
Grade 1 - Mild
Grade 2 - Moderate
Grade 3 - Pronounced
Grade 4 - Severe
Give the AOA classification of a Cortical Cataract
% of pupillary space affected
Grade 1 - 10%
Grade 2 - 10-50%
Grade 3 - 50-90%
Grade 4 - >90%
Give the AOA classification of Posterior Subcapsular Cataract
% of capsular area
Grade 1 - 3%
Grade 2 - 30%
Grade 3 - 50%
Grade 4 - >50%
Describe a traumatic cataract
Trauma causing a change in lens permeability
Imemdiate or delayed reaction (years)
Look for cataract to be unilateral
Other signs include a ruptured capsule and lens dislocation
What are all the associated conditions with traumatic cataracts/phakoanaphylactic uveitis
Describe a Vossius' ring cataract
With trauma the lens capsule may not rupture, instead ring of iris pigment deposited on the anterior lens surface
Describe Rosette cataract
A kind of cortical cataract, seen at posterior lens capsule (thinnest part of capsule)
Due to trauma, lens fibers begin to dissolve along the line of their pattern of growth
What is Exfoliation
Lens capsule rupturing due to trauma
Cortical material escapes into aqueous and an opacity forms
Lens protein is now recognized by the immune system as a foreign substance causing phakoanaphylactic uveitis
Describe Siderosis Lentis
Caused by an IRON foreign body penetrating the lens
Rust results underneath the capsule leading to a complete cortical cataract
Describe Chalcosis Lentis
Excessive amount of COPPER in the eye
Small yellowish-brown opacities in subcapsular cortex of lens and pupillary zone with a petal-like spoke that extends towards the equater
Can cause a green to reddish brown discoloration
Shows as a Sunflower Cataract
What can cause a Chalcosis Lentis?
Intraocular foreign body containg copper
Eyedrops containing copper sulfate
Manamgent is removal of the foreign body
What is subluxation?
Due to trauma, zonules rupturing allowing the lens to be pulled to one side
an INCOMPLETE lens detachment
What is a Luxation?
COMPLETE detachment of the lens, may dislocate anteriorly and posteriorly
Best choice is to shift posteriorly, lay the patient back; this is to keep the TM open
Describe the two dermatologic cataracts
Anterior shield like
These occur with skin conditions such as eczema (atopic dermatitis) and scleroderma
Describe diabetic cataracts
Type II (late onset) - will develop a senescent cataract earlier than normal
Type I - "Snowflake cataracts" limited to juvenile diabetics
Opacification occurs because of high sugar levels leading to high aqueous sugar levels that diffuse into the lens and is converted to alcohol creating a hypertonic environment
Describe Retinitis Pigmentosa
Hereditary retinal dystrophy
Refers to group on inherited conditions involving a reduced VF and night blindness
Posterior subcapsular cataract develops in the late stage
What kinds of cataract can occur with radiation and energy?
Infra-red/Glass blower's cataract
Describe an Infra-red Cataract
"Glass blower's cataract"
Due to a lack of eye protection
Iris absorbs heat and transfers it to the lens, you're cooking the lens.
Lens turns white, capsule exfoliates, splits and curls up into the anterior chamber
Describe a cataract induced by an X-ray/gamma rays
Seen with survivors of nuclear warfare
Develops 1-2 years after incident
Also found in cancer patients in radiation therapy
The radiation interferes with dividing cells at lens equator
Describe an electric shock induced cataract
Cortical cataract due to heat, concussion of the shock and/or electrolytic dissociation
Describe cataracts that are secondary to medication
Steroids cause PSC cataracts
Phenothiazines used in anti-psychotics cause stellated subcapsular cataracts (anterior/posterior)
Describe ECCE Cataract surgery
Extrasubcapsular Cataract Extraction --> Removal of the lens nucleus
Describe ICCE Cataract surgery
Intracapsular Cataract Extraction --> Entier lens is removed including the capsule